Chemometrics (eBook)
432 Seiten
Wiley-VCH (Verlag)
978-3-527-84379-4 (ISBN)
Explore chemometrics from basic statistics to the latest artificial intelligence and neural network developments in this new edition
Chemometrics is an area of study combining chemistry and mathematics. It governs the interpretation of data generated by chemical analysis, and its growth as a subfield promises to streamline and revolutionize analytical chemistry.
Chemometrics has long been the leading introductory textbook in this subject. Beginning with an introduction to the statistical-mathematical evaluation of chemical measurements, it leads readers through modern chemometric approaches in a pedagogically sound and highly readable style. Now fully updated to reflect the latest research and applications of this exciting discipline, it provides essential tools for a new generation of analytical chemists.
Readers of the fourth edition of Chemometrics will also find:
- New or expanded treatment of subjects such as deep learning, ANNOVA simultaneous component analysis, instrumental data output, and more
- Detailed discussion of approaches to signal processing, design and optimization of experiments, pattern recognition and classification, and many other areas
- Balance of theoretical and practical knowledge to enable rapid application of key techniques
Chemometrics is ideal for advanced students in chemistry, analytical chemistry, pharmaceutical chemistry, biochemistry, or related subjects, and as a useful reference for practicing researchers and laboratory professionals.
Matthias Otto is Professor Emeritus of Analytical Chemistry at the TU Bergakademie Freiberg in Germany. He conducted his studies at the University of Leipzig before accepting a role as lecturer in Freiberg, Germany, where he was appointed full Professor in 1987. He has taught almost all aspects of analytical chemistry, mainly within the curricula of chemistry, applied sciences, and geoecology, and has organized courses in basic and advanced chemometrics.
Matthias Otto is Professor emeritus of Analytical Chemistry at the TU Bergakademie Freiberg in Germany. He studied at the University of Leipzig. In 1984 he moved to Freiberg (Germany) as a lecturer and was appointed full Professor there in 1987. He has taught almost all aspects of analytical chemistry, mainly within the curricula of chemistry, applied sciences and geoecology, and organizes courses in basic and advanced chemometrics. He is author and editor of successful textbooks in analytical chemistry.
Contents
List of Abbreviations VII
Symbols IX
1 What is Chemometrics?
1.1 The Computer-Based Laboratory
1.2 Statistics and Data Interpretation
1.3 Computer-Based Information Systems/Artificial Intelligence
General Reading
Questions and Problems
2 Basic Statistics
2.1 Descriptive Statistics
2.2 Statistical Tests
2.3 Analysis of Variance
General Reading
Questions and Problems
3 Signal Processing and Time Series Analysis
3.1 Signal Processing
3.2 Time Series Analysis
General Reading
Questions and Problems
4 Optimization and Experimental Design
4.1 Systematic Optimization
4.2 Objective Functions and Factors
4.3 Experimental Design and Response Surface Methods
4.4 Sequential Optimization: Simplex Method
General Reading
Questions and Problems
5 Pattern Recognition and Classification
5.1 Preprocessing of Data
5.2 Unsupervised Methods
5.3 Supervised Methods
General Reading
Questions and Problems
6 Modeling
6.1 Univariate Linear Regression
6.2 Multiple Linear Regression
6.3 Nonlinear Methods
General Reading
Questions and Problems
7 Analytical Databases
7.1 Representation of Analytical Information
7.2 Library Search
7.3 Simulation of Spectra
General Reading
Questions and Problems
8 Knowledge Processing and Soft Computing
8.1 Artificial Intelligence and Expert Systems
8.2 Neural Networks
8.3 Fuzzy Theory
8.4 Genetic Algorithms and Other Global Search
Strategies
General Reading
Questions and Problems
9 Quality Assurance and Good Laboratory Practice
9.1 Validation and Quality Control
9.2 Accreditation and Good Laboratory Practice
General Reading
Questions and Problems
Appendix
Index
1
What is Chemometrics?
Learning Objectives
- To define chemometrics
- To learn how to count with bits and how to perform arithmetic or logical operations in a computer
- To understand the principal terminology for computer systems and the meaning of robotics and automation.
The development of the discipline of chemometrics is strongly related to the use of computers in chemistry. Some analytical groups in the 1970s were already working with statistical and mathematical methods that are ascribed nowadays to chemometric methods. Those early investigations were connected to the use of mainframe computers.
The notation chemometrics was introduced in 1972 by the Swede Svante Wold and the American Bruce R. Kowalski. The foundation of the International Chemometrics Society in 1974 led to the first description of this discipline. In the following years, several conference series were organized, for example, Computer Application in Analytics (COMPANA), Computer‐Based Analytical Chemistry (COBAC), and Chemometrics in Analytical Chemistry (CAC). Some journals devoted special sections to papers on chemometrics. Later, novel chemometric journals were started, such as the Journal of Chemometrics (Wiley) and Chemometrics and Intelligent Laboratory Systems (Elsevier).
An actual definition of chemometrics is:
the chemical discipline that uses mathematical and statistical methods, (a) to design or select optimal measurement procedures and experiments, and (b) to provide maximum chemical information by analyzing chemical data.
The discipline of chemometrics originates in chemistry. Typical applications of chemometric methods are the development of quantitative structure–activity relationships and the evaluation of analytical–chemical data. The data flood generated by modern analytical instrumentation is one reason that analytical chemists, in particular, develop applications of chemometric methods. Chemometric methods in analytics are a discipline that uses mathematical and statistical methods to obtain relevant information on material systems.
With the availability of personal computers at the beginning of the 1980s, a new age commenced for the acquisition, processing, and interpretation of chemical data. In fact, today, every scientist uses software, in one form or another, that is related to mathematical methods or processing of knowledge. As a consequence, the necessity emerges for a deeper understanding of those methods.
The education of chemists in mathematics and statistics is usually unsatisfactory. Therefore, one of the initial aims of chemometrics was to make complicated mathematical methods practicable. Meanwhile, the commercialized statistical and numerical software simplifies this process, so that all important chemometric methods can be taught in appropriate computer demonstrations.
Apart from the statistical–mathematical methods, the topics of chemometrics are also related to problems of the computer‐based laboratory, to methods for handling chemical or spectroscopic databases, and to methods of artificial intelligence.
In addition, chemometricians contribute to the development of all these methods. As a rule, these developments are dedicated to particular practical requirements, such as the automatic optimization of chromatographic separations or in prediction of the biological activity of a chemical compound.
1.1 The Computer‐Based Laboratory
Nowadays, the computer is an indispensable tool in research and development. The computer is linked to analytical instrumentation; it serves as a tool for acquiring data, word processing, and handling databases and quality assurance systems. In addition, the computer is the basis for modern communication techniques such as electronic mails or video conferences. In order to understand the important principles of computer usage, some fundamentals are considered here, that is, coding and processing of digital information, the main components of the computer, programming languages, computer networking, and automation processes.
Analog and Digital Data
The use of digital data provides several advantages over the use of analog data. Digital data are less noise sensitive. The only noise arises from round‐off errors due to finite representation of the digits of a number. They are less prone to, for instance, electrical interferences, and they are compatible with digital computers.
As a rule, primary data are generated as analog signals either in a discrete or a continuous mode (Figure 1.1). For example, monitoring the intensity of optical radiation by means of a photocell provides a continuous signal. Weak radiation, however, could be monitored by detecting individual photons with a photomultiplier.
Figure 1.1 Signal dependence on time of an analog (a) and a digital detector (b).
Usually, the analog signals generated are converted into digital data by an analog‐to‐digital converter (ADC) as explained as follows:
Binary versus Decimal Number System
In a digital measurement, the number of pulses occurring within a specified set of boundary conditions is counted. The easiest way to count is to have the pulses represented as binary numbers. In this way, only two electronic states are required. To represent the decimal numbers from 0 to 9, one would need 10 different states. Typically, the binary numbers 0 and 1 are represented electronically by voltage signals of 0.5 and 5 V, respectively. Binary numbers characterize coefficients of the power of 2, so that any number in the decimal system can be described.
Example 1.1 Binary Number Representation
The decimal number 77 is expressed as binary number by 1001101, that is,
1 | 0 | 0 | 1 | 1 | 0 | 1 |
1 × 26 | 0 × 25 | 0 × 24 | 1 × 23 | 1 × 22 | 0 × 21 | 1 × 20 = |
64 | +0 | +0 | +8 | +4 | +0 | +1 = 77 |
Table 1.1 summarizes further relationships between binary and decimal numbers. Every binary number is composed of individual bits (binary digits). The digit lying farthest to the right is termed the least significant digit, and the one on the left is the most significant digit.
Table 1.1 Relationship between binary and decimal numbers.
Binary number | Decimal number |
---|
0 | 0 |
1 | 1 |
10 | 2 |
11 | 3 |
100 | 4 |
101 | 5 |
110 | 6 |
111 | 7 |
1000 | 8 |
1001 | 9 |
1010 | 10 |
1101 | 13 |
10 000 | 16 |
100 000 | 32 |
1 000 000 | 64 |
How are calculations done using binary numbers? Arithmetic operations are similar but simpler than those for decimal numbers. In addition, for example, four combinations are feasible:
0 | 0 | 1 | 1 |
---|
+0 | +1 | +0 | +1 |
0 | 1 | 1 | 10 |
Note that for the addition of the binary numbers 1 plus 1, a 1 is carried over to the next higher power of 2.
Example 1.2 Calculation with Binary Numbers
Consider the addition of 21 + 5 in the case of a decimal (a) and of a binary number (b):
a. | 21 | b | 10101 |
+5 | 101 |
26 | 11010 |
Apart from arithmetic operations in the computer, logical reasoning is necessary too. This might be in the course of an algorithm or in connection with an expert system. Logical operations with binary numbers are summarized in Table 1.2.
Table 1.2 Truth values for logical connectives of predicates p and q based on binary numbers.
p | q | p AND q | p OR q | IF p THEN q | NOT p |
---|
1 | 1 | 1 | 1 | 1 | 0 |
Erscheint lt. Verlag | 28.11.2023 |
---|---|
Sprache | englisch |
Themenwelt | Naturwissenschaften ► Chemie |
Schlagworte | Analytical Chemistry • Analytische Chemie • Biostatistics • Biostatistik • Chemie • Chemische Analyse • Chemistry • Chemometrik • Industrial Chemistry • Statistics • Statistik • Technische u. Industrielle Chemie |
ISBN-10 | 3-527-84379-5 / 3527843795 |
ISBN-13 | 978-3-527-84379-4 / 9783527843794 |
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